Ruby “gem generate” indexer broken with XML Builder 3.0.0. How to fix?

Question

Problem: gem generate fails because it's missing XML Builder.

$ gem generate
  ERROR:  While executing gem ... (RuntimeError)
    Gem::Indexer requires that the XML Builder library be installed:
      gem install builder

How to fix this?

Answer 1

I found a solution: edit rubygem source code file indexer.rb to require the older Builder.

gem 'builder', '~> 2.1'
require 'builder/xchar'